Mac OS X has a couple of great safeguards in place to prevent you from accidentally running malicious applications that might infect or otherwise damage your computer. But that can occasionally also prevent perfectly legitimate applications from running.
Here's how to keep your computer safe and also have the option to open certain software on a case-by-case basis.
What Mac safeguards keep me protected?
First introduced in OS X Mountain Lion, Gatekeeper looks at a program when you run it to determine whether it meets a few criteria set by the system. If it meets those settings, the app runs; if not, the computer refuses to open the application.
How to change your Gatekeeper settings
Gatekeeper offers three different security settings for users regarding the opening of applications.
By default, OS X prefers Mac App Store-only applications. As such, if the app you're trying to open has been downloaded from the Mac App Store, it's automatically approved, as Apple does security checks on all applications before approving them for sale in the store.
But there are two other options available to you: allowing apps from the Mac App Store and registered developers, or allowing any application developed for the Mac — no matter who or where it's from.
To change this setting, visit the System Preferences app and click on the Security & Privacy icon. From there, you'll see a section under General that asks what kinds of apps you'd like to allow: only apps downloaded from the Mac App Store, apps from the Mac App Store and registered developers, or any application developed for the Mac.
If you choose Mac App Store and identified developers, that means you'll be able to run apps both from the store and any whose developers have received a security certificate from Apple and have digitally signed their app with that certificate.
If your app was created and signed by an identified developer, your system can tell who developed it, if it's been tampered with, and shut the app down if necessary. OS X checks in with Apple's servers once a day to make sure your apps' certificates are valid; if something's happened to a developer's app, Apple can add the developer's certificate to a blacklist, which then propagates to your computer and prevents the offending application(s) from opening.
If you choose the option for running any application, Gatekeeper effectively shuts down, trusting you to police your own software. I tend not to recommend this option: Even though there haven't been too many malicious apps created for the Mac, those security protocols exist for a reason.
Okay, but what if I've got an app from a non-identified developer that I want to run?
Never fear! There's an easy way to run apps from non-identified developers or the Mac App Store. Just follow these simple steps. Remember, if you want to run a piece of software from an unidentified developer, make absolutely sure you know where it came from.
- Download the piece of software you wish to run and drag it to your Applications folder.
- Control-click or right-click the application icon and select Open.
- When you do, you'll see a pop-up asking if you'd like to open this app. Once you press Open, the app will launch.
From here on out, your Mac will remember that you've allowed this app to run, and you won't see any more pop-up requests or warnings.